Intensities Of Spectral Components Research Articles

Specific features of the radial distributions of plasma parameters in the initial segment of a supersonic jet generated by a pulsed capillary discharge

Results are presented from spectroscopic studies of the initial segment of a supersonic plasma jet generated by a pulsed capillary discharge with an ablative carbon-containing polymer wall. Specific features of the spatial distributions of the electron density and intensities of spectral components caused, in particular, by the high electron temperature in the central zone, much exceeding the normal temperature, as well as by the high nonisobaricity of the initial segment of the supersonic jet, are revealed. Measurements of the radiative properties of the hot jet core (the intensity and profile of the Hα and Hβ Balmer lines and the relative intensities of C II lines) with high temporal (1–50 μs) and spatial (30–50 μm) resolutions made it possible to determine general features of the pressure and temperature distributions near the central shock. The presence of molecular components exhibiting their emission properties at the periphery of the plasma jet allowed the authors to estimate the parameters of the plasma in the jet region where “detached” shock waves form.

Prospects for Development of Noninvasive Spectrophotometric Medical Diagnosis

Analysis of the development of modern medical diagnosis and treatment shows that there is a worldwide trend toward introduction into medical practice of sophisticated scientifically substantiated methods minimizing invasiveness, radiation load, and other physiologically and psychologically undesirable effects. Modern electronic, laser, and computer technologies, etc. are used to increase the efficiency of diagnosis and treatment. Population growth and rising incidence of many diseases increase the load on medical personnel, making it necessary to develop highly efficacious medical technologies providing minimal time per examination. These requirements are fully met by noninvasive (in vivo) laser and other optical methods of diagnosis, which have been extensively used in many industrially developed countries for the last 10-15 years [8, 11, 13]. These methods are based on the use of low-intensity (up to 10†mW) optical radiation for examination of organs and tissues. The light reflected by or transmitted through the tissues provides diagnostic information about their state. Processes of linear and quasi-linear interaction of light with optically inhomogeneous and semitransparent media (lymph, soft tissues, etc.) form the physical basis of these diagnostic methods [21]. For example, a light beam falling on skin is partially reflected by it and partially transmitted, reaching the connective and muscular tissues, vascular bed, etc. The transmitted radiation is multiply reflected (scattered) within biological tissues on the boundaries of inhomogeneous anatomical and cellular structures and partially absorbed by different substances (water, melanin, hemoglobin, etc.). A part of the radiation attenuated by absorption and multiple scattering emerges back from the skin surface [13], forming so-called back-scattered radiation flux Fbs. A small part of radiation is transmitted through the organ under examination. It forms the transmitted radiation flux Fτ. These fluxes can be detected using a photodetector. Different spectral components of optical radiation are absorbed and scattered by different biological tissues and substances. Thus, exposure of various organs and areas of human body to radiation of given intensity and spectral composition with further analysis of the intensities of spectral components of the fluxes Fbs and/or F τ provide valuable information about the internal structure of the organ under examination. The principles outlined above are already imple

Correlation between the Intensities of Spectral Components of 1/f Noise

We analyze the estimate of the correlation factor between noise intensities at the outputs of two bandpass filters as a parameter that allows us to obtain additional information on the nature of the 1/f noise. The confidence interval is calculated for the experimental evaluation of the correlation factor between readings of noise intensities. Data on noise in GaAs films and also for the numerical model of the 1/f noise as a superposition of telegraphic random processes are presented and discussed.

Photoluminescence of excitons bound to the isoelectronic hydrogen-related defects B711 (1.1377 eV) in silicon.

Photoluminescence (PL) spectra of excitons bound to the isoelectronic defects ${\mathit{B}}_{71}^{1}$ (1.137 68 eV principal no-phonon line) created in phosphorus-doped silicon grown in a hydrogen atmosphere as a result of irradiation by thermal neutrons were investigated in magnetic fields up to 12 T and under uniaxial stress. The ${\mathit{C}}_{3\mathit{V}}$ symmetry of these defects was determined unambiguously from the dependences of the Zeeman splitting and the intensities of spectral components on magnetic-field orientation. The ground state of the bound exciton is split into a doublet with approximately 30 \ensuremath{\mu}eV energy separation. This splitting, which is not evident in the zero-field spectra because of the selection rules, results in the appearance of an additional spectral component in a magnetic field. Using group theoretical methods we constructed a Hamiltonian for excitons bound to the ${\mathit{B}}_{71}^{1}$ isoelectronic center, which takes into account electron-hole coupling and interaction with external perturbations. The phenomenological parameters of this Hamiltonian were determined from the optimal fit between theoretical and experimental dependences of the PL peak positions and their amplitudes on magnetic field and uniaxial stress. The proposed model of these bound excitons explains all of our experimental observations.